1. Field of Invention
Aspects of this invention are related generally to endoscopic imaging and are more particularly related to capturing light from a common front end optical structure in a plurality of coplanar image capture sensors.
2. Related Art
The da Vinci® Surgical Systems, commercialized by Intuitive Surgical, Inc., Sunnyvale, Calif., are minimally invasive teleoperated surgical systems that offer patients many benefits, such as reduced trauma to the body, faster recovery and shorter hospital stay. One key component of a da Vinci® Surgical System (e.g., the model IS3000, da Vinci® Si HD) is a capability to provide two-channel (i.e., left and right) video capture and display of visible images to provide stereoscopic viewing for the surgeon. Such electronic stereoscopic imaging systems may output high definition video images to the surgeon, and may allow features such as zoom to provide a “magnified” view that allows the surgeon to identify specific tissue types and characteristics, as well as to work with increased precision.
Typically in a minimally invasive surgical system, an image capture system is coupled to a proximal end (away from the surgical site) of a stereoscopic endoscope. However, some stereoscopic endoscopes have included image capture components in the distal end (nearest the surgical site) of the endoscope. FIGS. 1A to 1D are examples of image capture sensor configurations in a distal end of a stereoscopic endoscope from U.S. Pat. No. 4,873,572 (filed Feb. 24, 1988).
In FIG. 1A, a distal end 100A of an endoscope includes a plate-like package 113A with a center line coinciding with a longitudinal axis 133A of the endoscope. Two charge coupled devices (CCDs) 114A1 and 114A2 are mounted on opposing surfaces of package 113A. Two objective lenses 115A1 and 115A2 are symmetrically arranged on both sides of longitudinal axis 133A of the endoscope. Mirrors 116A1, 116A2 are symmetrically arranged on the optical axis of the respective objective lenses 115A1, 115A2. Light reflected from an object external to the endoscope passes through objective lens 115A1, 115A2 and is reflected by mirrors 116A1, 116A2 onto the imaging surfaces of CCDs 114A1 and 114A2. The video signals from CCDs 114A1 and 114A2 are transmitted to a video processor external to the endoscope.
In FIG. 1B, a distal end 100B of an endoscope includes two objective lenses 115B1, 115B2 arranged the same as objective lenses 115A1 and 115A2 in FIG. 1A. Mirrors 116B1 and 116B2 are mounted with the mirror surfaces parallel to and removed from longitudinal axis 133B of the endoscope. Light reflected from an object external to the endoscope passes through objective lenses 115B1, 115B2 and is reflected by mirrors 116B1, 116B2 to refracting prisms 117B1, 117B2. The optical path from prisms 117B1, 117B2 is to the imaging surfaces of CCDs 114B1, 114B2. CCDs 114B1 and 114B2 are mounted so that the imaging surfaces of CCDs 114B1, 114B2 intersect at right angles with the optical axis of the optical path from prisms 117B1, 117B2, respectively. Thus, CCD 114B1 and 114B2 are each mounted with the imaging surface inclined at a predetermined angle with respect to longitudinal axis 133B of the endoscope.
In FIG. 1C, two objective lenses 115C1 and 115C2 are eccentric, for example, to the upper side from the center axis of the lens. Reflecting prisms 117C1 and 117C2 are arranged on the optical axes of the respective objective lenses 115C1 and 115C2. The centers of Prisms 115C1 and 115C2 are positioned at a same height as the respective objective lenses 115C1 and 115C2, but are somewhat displaced in the horizontal direction. Prism 117C1 is somewhat displaced to the left from objective lens 115C1 and the prism 117C2 is somewhat displaced to the right from objective lens 115C2.
The light reflected by each of prisms 117C1 and 117C2 is reflected by the respective slopes of prism 118C to form an image on the imaging surface of CCD 114C fitted to package 113C. Video signals from CCD 114C are transmitted to a video processor external to the endoscope.
In FIG. 1D, a distal end 100D of an endoscope includes two eccentric objective lenses 115D1, 115D2 arranged the same as objective lenses 115C1 and 115C2 in FIG. 1C. The positions of prisms 117D1 and 117D2 are displaced forward and rearward in comparison to prisms 117C1 and 117C2 in FIG. 1C. The light from prisms 117D1 and 117D2 is reflected respectively by mirrors 118D1 and 118D2 to form respective images on CCDs 114D1 and 114D2 mounted adjacently on package 113D, which is parallel to longitudinal axis of the endoscope.
One mirror 118D1 is concave and so forms an image on CCD 114D1 for a somewhat shorter optical path length than the optical path length for the image on CCD 114D2. Hence, in this example, the left optical channel has a shorter optical path length than the right optical channel. Video signals from CCDs 114D1 and 114D2 are transmitted to a video processor external to the endoscope.
FIGS. 1A to 1D illustrate a few ways of capturing a stereo image in the constrained space of an endoscope tip. But since a small outer diameter of the endoscope distal end is desirable, the configurations in these figures also illustrate how difficult it is to capture high quality stereoscopic images in small outer diameter distal-end image capture systems due to many problems.
Consider the configuration in FIG. 1A. To focus this device one has to move the tiny lenses of both objective lenses 115A1 and 115A2 very precisely to obtain focus. The configuration in FIG. 1B suffers from needing to bend the light at an odd angle with a prism. This likely leads to lateral color distortion and uneven performance on the left and right image sensors. The images are not optimally spaced.
The configurations in FIGS. 1C and 1D require the image to lie flat in the plane of the optics. Either the CCD or the optical components cannot lie on the mid-plane of a round endoscope tip thus these configurations require either very small optical components (and a small inter-pupillary distance) or a very small CCD which limits the imaging quality as the area is small thus restricting the number of pixels and/or the pixel size. Also, in the configuration of FIG. 1D, the optical path lengths have different lengths, and so the optical components for each channel must be different.